Growing Tips: Lobelia

Quick Reference:

Annual, a plant that completes it’s life cycle in one season. Germinates in 15 to 20 days at an optimum soil temperature of 70 degrees F. DO NOT cover seed, it requires light for germination. Seed spacing ¼ to ½ inch. Ideal garden spacing for the trailing variety is 4 to 6 inches. The compact mounded variety is 8 to 12 inches.

When and where to plant:

Lobelia is a very slow growing plant that must be started indoors 10 to 12 weeks before the last frost to assure bloom all summer in Alaska. Fill a container that has drainage holes with a sterilized potting soil, sprinkle the very small seed on soil surface, DO NOT cover and water well for good seed-soil contact. Cover the container with clear plastic, keep warm and moist until seedlings emerge. Remove the plastic as soon as the seedlings start to sprout. When the seedlings show their first green leaves water with a liquid solution of plant food. As soon as the tiny seedlings reach their 3-4 leaf stage transplant 3 or 4 seedlings in individual 2" plastic pots, grow in partial shade where the night temperature is 50 to 55 degrees F, keep the soil evenly moist and water with a liquid solution of plant food every two weeks until the garden is ready. Lobelia transplants easily. Select sunny or lightly shaded location with a rich, well-drained sandy soil and plant outdoors after the danger of frost is past.


Keep soil uniformly moist. Apply a liquid solution of plant food after first blooming period and then every 2 to 3 weeks for continuous bloom all summer.